Electrothermal pyrolysis of oil shale



April 9, 1968 v l. s. SALNIKOV ELECTROTHERMAL PYROLYSIS OF OIL SHALE Filed Oct.

INVENTOR. IVAN S. SALNIKOV ATTORNEY United States Patent 3,377,266 ELECTROTHERMAL PYROLYSIS OF OIL SHALE Ivan S. Salnikov, 1830 Zinnia,

Golden, Colo. 80401 Filed Oct. 12, 1964, Ser. No. 403,315

Claims. (Cl. 208-11) This invention relates to a novel and improved method and apparatus for retorting oil shale and carbonaceous materials of similar characteristics, and more particularly relates to an electrothermal method and apparatus for the pyrolysis of oil shale to recover shale oil therefrom in a highly efiicient and economical manner.

Various processes have been devised for use in the pyrolysis of shale rocks in order to decompose the organic material, or kerogen, and recover the shale oil values therefrom; and specifically such processes have been devised to the end of realizing maximum oil recovery at the least cost. In practice, however, for the most part processes evaluated to the present time have not demonstrated themselves to be economically feasible due to their relatively high cost of operation and handling and especially due to heat energy requirements and high cost of production in remote locations where the shale is mined and processed. Furthermore, difficulties have been experienced in effectively separating the shale oil from the other products of distillation or pyrolysis without requiring further expensive treatment. Therefore, it is highly desirable that the means employed for transferring heat to the shale rock during pyrolysis be thermally selfsustainin-g, .or in other words, be capable of being replenished from the residual matter in the shale without resorting to outside sources of power or to use of the oil recovered; and that it be closely controlled to produce high yields of oil with a minimum percentage of impurities thus lending itself well to rapid and efiicient recovery of shale oil.

Accordingly, it is a principal and foremost object .of the present invention to provide for a novel and improved method and means for electrothermal pyrolysis of oilshale, and to carry .out the method in such a way that operating costs of production are held at a minimum while realizing maximum recovery of shale oil therefrom. 7

Another object of the present invention is to provide ,a process and apparatus for destructive distillation of oil shale and the like which is highly efiicient and economical in operation and is further characterized by maximum utilization of the heat energy available from the residual matter in the shale remaining after pyrolysis to provide an ample source of heat and power for continuous operation of the apparatus thereby eliminating the need for an outside source of power.

It is a further object .of the present invention to pro- Ivide for the electrothermal distillation of shale oil from the shale rock which is both rapid and continuous and will insure uniform and thorough heating of the shale 'rock to recover maximum percentages of shale oil therefrom, and specifically in such a way as to enable the closely controlled, selective distillation of the hydrocarbon oils while minimizing formation of gases or vapors from the residual or fixed carbon and other impurities in the rock.

It is a still further object of the present invention to v provide in the destructive distillation of oil shale for ,is characterized by utilization of electric energy in the pyrolysis of oil shale fed successively, and in a continuous manner through a preheat zone and pyrolysis zone in the absence of air; thereafter, the spent shale and specifically the residual carbon matter in the shale, is utilized to create sufiicient heat energy for conversion to electrical energy as required for pyrolysis; and wherein the electrical energy supplied during pyrolysis is closely controllable within the required temperature range for most effective distillation. Moreover, the gaseous products of distillation are directed through the preheat zone to transfer heat to the incoming shale and a portion .of the non-condensable gases recovered may be recycled through the preheat zone to minimize condensation of the distillation products when cooled in passing through the preheat zone. In addition, the apparatus is characterized by the construction and arrangement of a series of electrical heating elements in the distillation zone or retort so disposed in relation to movement of the shale as to permit continuous travel of the shale therethrough while effecting direct, uniform and thorough heating of the shale for the necessary length of time to insure most complete distillation; and furthermore wherein the heating elements may be rapidly removed, cleaned and replaced with minimum loss in time, and in operation can be closely controlled to supply the necessary heat for rapid and substantially complete and selective distillation .of the hydrocarbon oils from the shale passing through the pyrolysis zone.

The above and other objects, advantages and features of the present invention will become more readily understood from the following description .of a preferred form of process and apparatus when considered in connection with the accompanying drawings in which:

FIGURE 1 is a somewhat schematic view of a preferred form of apparatus and system for use in shale pyrolysis with the retort thereof being shown in section; and

FIGURE 2 is a horizontal section view taken about lines 2- 2 of FIGURE 1 and illustrating the spacing and arrangement of the heating elements employed in the apparatus.

Referring in detail to the drawing, there is shown by way of illustrative example a vertical furnace or retort I10 of hollow, elongated cylindrical configuration and which is formed to define in downward succession a preheat zone 12, a distillation zone 13, and a lower heat exchange zone 14. In construction, the retort 10 preferably consists of a pair of heavy walled, upper and lower tubular sections 17 and 18 connected in end-toend relation by means of abutting flanges 19 interconnected 'by suitable bolts 20. To form the preheat zone 12, the upper tubular section 17 includes an upwardly convergent wall portion 22 for connection in end-to-end relation with a tubular section 24, of reduced size, again through abutting flanges 25 being interconnected by suitable bolts 26. The top tubular portion 24 also defines the entranceinto the preheat zone from the top of the furnace and for this purpose is provided with a central opening 28 for'insertion of a generally funnel-shaped hopper 30 in which is disposed an auger 32, the latter being driven by an electric motor 33 through gear drive 34 and drive shaft 35.

In order to separate the tubular section into spaced upper and lower chambers, the lower tubular section 18 has an internal annular shoulder '38 just beneath its point of connection to the upper tubular section 17 which serves to support a downwardly convergent wall portion 40 in cluding a lower tubular portion 42 of reduced size for sealed chamber for passage of shale at a controlled rate v of travel through the preheat zone and distillation zone. Similarly, the lower end of the tubular section 18 has a convergent wall portion 44 extending downwardly into a lower tubular portion 46 for an ejection screw or auger 4-7, and it will be noted that the augers 43 and 47 are driven through a common drive shaft 48 by electric motor 49 through gear train 50. In general, the various tubular sections and wall portions are heavy-walled and in a conventional manner are surfaced with an inner, refractory lining, not shown, so as to be capable of withstanding the intense heat developed within the furnace during pyrolysis of the shale.

An important feature of the present invention resides in the construction and arrangement of the heating elements employed in the distillation or pyrolysis zone 13; and in the preferred form of apparatus a nest or series of electrical resistance heating elements 52 are arranged in spaced parallel relation to one another in the zone with each element being disposed on an axis parallel to the path of fiow of the shale material through the retort. Preferably, each heating element is defined by an elongated, cylindrical rod 54 of metallic material having an outer jacket 55 composed of a suitable fire clay or ceramic material whose expansion and contraction characteristics correspond with that of the material defining the rods 54. The heating elements 52 are supported in vertical, spaced relation within the distillation zone by means of an open grid or mounting frame 56 having intersecting cross bars 58 and an outer circular ring 59; and the frame 56 is remov-ably seated in horizontal relation across the distillation zone upon an inwardly projecting annular shoulder 60 at the upper end of the tubular section 18 and is held firmly in place by means of another internal shoulder 62 at the lower extremity of the tubular section 17, the latter engaging the ring 59 on the mounting plate when the tubular sections are secured in connected together relation as illustrated. Preferably each heating element 52 has a lower threaded end 64 for threaded insertion into a socket 65, there being a plurality of sockets 65 provided at uniformly spaced intervals and in upwardly facing relation on the mounting frame, as best seen from FIGURE 2, to support the heating elements in desired spaced relation for upward extension through the distillation zone. Moreover, as represented, electrical wire cable network 68 is imbedded within the mounting frame to establish electrical connection from a main power line 70 to each of the sockets 65 and, in turn, to each of the respective heating elements 52.

It will be seen that the entire heating assembly including the heating elements 52 and the mounting frame 56 may be removed from the chamber by removing the top tubular section 17; and a detachable manhole cover 72 is positioned over one open side of the upper tubular section 17 to afford access to the heating assembly so that the heating elements can be individually removed or replaced without disassembling the entire apparatus.

From the foregoing description of a preferred form of retort, it is believed that the accessory equipment utilized in association therewith may be best described by referring to a preferred mode of carrying out the process of the present invention. In the process, particles of crushed oil shale S, for example, marlstone crushed to a size of inch to 2 inches in diameter are conveyed to the hopper at the top of the furnace by suitable means and caused to descend slowly in succession through the preheat zone 4 in the direction of movement of the shale material through the distillation zone, will establish direct contact with the material throughout a substantial portion of its travel through the chamber so as to bring about most uniform and thorough heating of the shale, and the outer protective jackets 55 will serve to insulate the rods from direct physical cont-act with the shale while effectively conducting the heat developed in the rods but without impeding the movement of the shale particles through the distillation zone. This arrangement is further advantageous in that the fire clay jackets, once heated to the elevated temperature required for distillation will not experience rapid temperature changes in heating the shale while being maintained at the high temperature level by the resistance heating rods. Thus, by heating the elements 52 to the elevated temperature level necessary to heat the distillation zone to the temperature of distillation of the shale oil-forming gases, this being on the order of 900- 1000 F, the shale particles will liberate hydrocarbon gases and vapors which for the most part are the shale oil-forming gases and which can be separately collected and recovered outside the furnace or retort in a well known manner. By excluding air from the distillation zone, the residual or fixed carbon in the shale will pass with the spent shale into the lower heat exchange zone, again at a controlled rate of travel as determined by the speed of rotation of the auger 43.

The vaporous products of distillation formed will rise in counter current fashion from the pyrolysis zone through the preheat zone in heat transfer relation to the incoming shale, then are recovered through gas line for removal through condensor 82 to an accumulator 84 for collection of the condensed shale oil with minor percentages of other condensed hydrocarbon vapors. The noncondensable gases will tend to rise in the accumulator through line 85 either for separate collection through branch line '86 or for recycling through line 88, and the proportionate flow between lines 86 and 88 may be suitably controlled by valves 89 and 90 in the respective lines. Of the recycled gases, a portion is drawn through line 92 and delivered by means of a blower, represented at 93, through line 94 to the preheat zone 12. In this way, the non-condensable gases will mix with the gaseous products of distillation rising from the distillation zone in order to raise the condensation level of the gases formed by pyrolysis and thereby to minimize condensation of the gases when cooled by the incoming shale.

Another portion of the recycled gases may be drawn through recycle line 88 as a source of fuel either in the heat exchange zone 14 or for a steam power plant 96. However, the main source of energy for the power plant 96 is derived from the heat exchange zone, and to this end a circulating coil 97 is directed in helical fashion upwardly through the heat exchange zone having a .water inlet 98 and a steam outlet 99 leading to the power plant 96. In this way, water circulated through the coil 97 is increasingly heated as it winds upwardly through the coil in contact with the progressively hotter shale bed moving downwardly through the heat exchange zone, until it is vaporized to form steam for discharge to the power plant. The steam power plant 96 is most desirably employed to operate a steam turbine therein or other suitable prime mover for an electric generator 100, thus converting the heat energy from the heat exchange zone to electric energy. The outlet power line 70 leads from the generator 100 to the wire network 68 in the frame 56 for heating the elements 52, and a rheostat 104 is positioned in the line to regulate the supply of current to the heating elements and consequently to establish close control over the temperature level developed in the distillation zone.

Heat transfer to the water circulated through the heat exchange coil is aided by combustion of the fixed or residual carbon in the shale, this being accomplished by directing air from a blower 107 through line 108 and Vent 109 to discharge the air upwardly through the downwardly flowing shale bed and promote combustion of the carbon; Thus, the heat of combustion developed from oxidation of the fixedor residual carbon will substantially increase the heat energy available for conversion of the water to steam supplied to the power plant in order to operate the electrical generator and provide a closed regenerative system for oil shale pyrolysis. The gases formed in the heat exchange zone are recovered through outlet line 112 located above the heat exchange zone.

The rate of travel of the spent shale through the lower heat exchange zone is controlled independently of its rate of travel through the upper zones by regulating the speed of rotation of the augers 43 and 47, and will permit direct introduction of the spent shale at an elevated temperature from the distillation zone into the heat exchange zone for most effective use in forming steam to generate electricity. Moreover, electrical power line 70 serves as a power source for the gas blower, air blower andelectrical motors for the feed screws so that the entire system is self-contained without resorting to outside power sources.

In practice, the heating elements are first heated to raise the temperature in the distillation zone to that required for pyrolysis, and this heating may be accomplished by use of a boiler, not shown, to supply the necessary steam for operation of the power plant until suflicient steam is generated in the heat exchange zone. Thereafter, the crushed oil shale particles are advanced downwardly through the furnace or retort for gravity flow in succession through a preheat zone where the shale is preheated by the oil-forming gases and vapors passing upwardly from the pyrolysis zone, then through the distillation zone where the particles are subjected to electrothermal pyrolysis; and again, by excluding air during pyrolysis the fixed carbon will for the most part remain undisturbed and the gasiform products of distillation will rise upwardly through the preheat zone and be blended with recycled-gas to minimize condensation, then are discharged for collection and recovery of the shale oil. From the distillation zone the spent shale is fed at a controlled rate into the lower heat exchange zone where the carbon matter is oxidized or combusted to provide, along with the hot spent shale, a source of heat energy for conversion to electrical energy both for the electrical heater assembly in the distillation zone and for the various blowers and motors employed in the system. Again, the oil-forming gases and vapors which are extracted are recovered in a liquid state by condensa tion, whereas in part the other gaseous hydrocarbons, that can be condensed only with great difiiculty at low temperatures, are preferably recycled as described through the preheat zone and to the steam power plant, and further may be delivered to the heat exchange zone and combusted together with the spent shale to provide additional heat energy therein.

In the process and apparatus, however, an important feature is thought to reside in the use of electrical heating elements, and their efficient utilization of the heat energy recovered from the spent shale in the heat exchange zone to effect uniform and thorough heating of the shale to the required temperature of distillation. The use of electrical heating elements avoids the necessity of constant replacement but nevertheless can be individually or collectively removed or replaced, as required for periodic repair or maintenance. By maintaining close control over the temperature in the distillation zone, pyrolysis is carried out within a narrow range of temperature and, in the absence of air, to rapidly distill the hydrocarbon oils with a minimum amount of cracking or formation of fixed carbon, thus avoiding subsequent difficulty and expensive separation of large amounts of impurities from the gases. Moreover, the rate of travel of the spent shale through the heat exchange zone is independently controlled as described to assure that sulficient heat energy is derived from the shale for conversion to electrical energy in maintaining the heater assembly at the elevated temperature level. Of course other forms of electrical heating elements may be employed in the manner prescribed in accordance with the present invention, such as for example, induction heating elements; and the particular means adopted for conversion of the heat energy produced to electrical energy may be suitably varied, again the primary objective being to effect most direct, uniform and thorough heating of the oil shale at the least cost with maximum recovery of oil therefrom.

Accordingly, it is to be understood that various modifications and changes may be made in the particular construction and arrangement of parts comprising the preferred form of apparatus as well as the sequence of steps followed in carrying out the preferred process without departing from the spirit and scope of the present invention, as defined by the appended claims and reasonable equivalents thereof.

What is claimed is:

1. A continuous process for destructively distilling oil shale rock to recover shale oil therefrom which comprises the steps of crushing the shale and passing it at a controlled rate of travel in succession through a preheat zone, and a distillation zone in which the crushed shale is heated to the temperature of distillation of the oil-forming gases in the shale by advancing the shale into direct heat transfer relation to a series of elongated heating elements arranged parallel to the path of travel of the shale while excluding air from the preheat and distillation zones, and thereafter positively advancing the shale from the distillation zone to a heat exchange zone in which the shale rock is combusted to produce additional heat energy.

2. A continuous process for destructively distilling oil shale rock to recover shale oil therefrom which comprises the steps of crushing the shale and passing it at a controlled rate of travel in succession through a preheat Zone to effect heating of the shale to a temperature at which evolution of its volatile constituents begins and, a distillation zone in which the crushed shale is heated to the temperature of distillation of the shale oil by direct contact with a series of electrical heating elements arranged in the path of travel of the shale therethrough while excluding air from the preheat and the distillation zones, positively advancing the shale from the distillation zone through a heat exchange zone at a controlled rate of travel independently of its rate of travel through the distillation zone, combusting the shale to produce energy of the heat exchange zone and followed by converting the heat energy of the shale to electrical energy for the electrical heating elements in the distillation zone.

3. An electrothermal 'process for recovering shale oil from shale rock comprising the steps of preheating the shale in crushed form to a temperature below that at which pyrolysis of the shale rock occurs, electrothermally heating the shale in the absence of air by direct contact with a series of electrical heating elements to volatilize the oil-forming gases and vapors, passing the oil-forming gases and vapors upwardly through the preheat zone to preheat the incoming shale, condensing the oil-forming gases and vapors to recover the oil therefrom and recycling any non-condensable gases and vapors through the preheat zone for mixture with the gases and vapors from the distillation zone, positively advancing the shale from the distillation zone to a heat exchange zone, oxidizing the carbon in the shale to produce additional heat energy, circulating water through the heat exchange zone in heat exchange relation to the shale for generation of steam, followed by converting the steam to electrical energy for electrothermal pyrolysis of the shale passing through the distillation zone.

4. An electrothermal process for recovering shale oil from shale rock comprising the steps of preheating the 7 shale in crushed form to a temperature below that at which pyrolysis of the shale rock occurs, electrothermally heating the shale in the absence of air by direct contact with a series of electrical heating elements to volatilize the oil-forming gases, passing the oil-forming gases and vapors upwardly in countercurrent relation' through the preheat zone for preheating the incoming shale, collecting the oil-forming gases to recover the oil therefrom, positively advancing the shale from the distillation zone to a heat exchange zone and combusting the residual carbon in the shale to produce additional heat, independently controlling the rate of travel of the shale through the distillation zone and the heat exchange zone, adjustably controlling the electrical energy supplied to the distillation zone circulating water through the heat exchange zone in heat exchange relation with the shale for generation of steam, followed by converting the heat energy of the steam to electrical energy for electrothermal pyrolysis of the shale passing through the distillation zone.

5. Apparatus for recovering shale oil from shale rock comprising an elongated vertical housing for passage of the shale in particle form therethrough, a wall portion dividing said housing into an upper sealed chamber, and a lower heat exchange chamber shale delivery means for introducing the shale at a controlled rate of travel through said upper chamber while excluding air from said upper chamber, advancing means being disposed in sealed relation to said wall portion for withdrawing the shale at a controlled rate of travel from said upper chamber for advancement through said heat exchange chamber, and a heater assembly including a series of electrical heating elements being arranged in spaced relation across said upper chamber on axes parallel to the direction of advancement of the shale therethrough.

6. Apparatus according to claim 5, said heater assembly further including a horizontally disposed open frame having a series of sockets disposed in spaced, upwardly facing relation therein, an electrical wire network in said frame connected to said sockets, and said heating elements each having a connecting end for removable connection to said sockets.

7. Apparatus according to claim 5, said heat exchange chamber including a water circulating coil and air blower means circulating air through said heat exchange chamber to combust the carbon matter in the shale thereby to produce additional heat energy in heat transfer relation to the water circulating coil for conversion of the water to steam, a steam power plant, and an electrical generator associated with said power plant to generate electricity for said heater assembly to maintain said electrical heating elements at a selected temperature level.

8. In a retort according to claim 5, each of said heating elements being defined by an elongated resistance heater having an outer protective jacket composed of a fire clay material.

9. In a retort according to claim 5, each of said heating elements being defined by elongated resistance heater rods, and an open frame member removably disposed across said housing for supporting said rods in spaced relation thereon.

10. Apparatus for recovering shale oil from shale rock comprising an elongated vertical housing for passage of the shale in crushed form therethrough, said housing having an upper sealed chamber defining an upper preheat zone and a lower pyrolysis zone, and a lower heat exchange chamber being isolate from said upper chamber, delivery means being disposed in sealed relation to said upper chamber for introducing the shale at a controlled rate of travel into the preheat zone, and advancing means being disposed in sealed relation between said upper and lower chambers for withdrawing the shale at a controlled rate of travel from the pyrolysis zone for advancement through said lower heat exchange chamber, recovery means above the preheat zone for removal of the gases formed during pyrolysis including a bypass line to recycle a portion of the gases through the preheat zone, and a nest of electrical heating elements removably disposed in said upper chamber and being arranged in spaced parallel relation to one another across the pyrolysis zone in the path of advancement of the shale therethrough, energy converting means in heat transfer relation to the shale advancing through said heat exchange chamber for converting the heat energy derived from the shale to electrical energy and conducting means for applying electrical energy from said energy converting means to said electrical heating elements including adjustable control means for regulating the level of electrical energy applied to said heating elements.

References Cited UNITED STATES PATENTS 1,538,954- 5/1925 Rosenthal 20l15 1,706,420 3/1929 Trent 20ll9 2,012,477 8/1935 Olson 4865 2,516,474 7/ 1950 Melsted 13-2.0 2,637,683 5/1953 Kassel 201-16 2,698,283 12/1954 Dalin 2.08-l1 2,814,587 11/1957 Van Dijck 20l16 2,832,725 4/ 1958 Scott 20l27 3,109,781 11/1963 Natland 2088 FOREIGN PATENTS 233,126 12/ 1944 Switzerland.

338,115 6/ 1921 Germany.

630,048 10/ 1949 Great Britain.

DANIEL E. WYMAN, Primary Examiner.

P. KONOPKA, Assistant Examiner. 

1. A CONTINUOUS PROCESS FOR DESTRUCTIVELY DISTILLING OIL SHALE ROCK TO RECOVER SHALE OIL THEREFROM WHICH COMPRISES THE STEPS OF CRUCHING THE SHALE AND PASSING IT AT A CONTROLLED RATE OF TRAVEL IN SUCCESSION THROUGH A PREHEAT ZONE, AND A DISTILLATION ZONE IN WHICH THE CRUSHED SHALE IS HEATED TO THE TEMPERATURE OF DISTILLATION OF THE OIL-FORMING GASES IN THE SHALE BY ADVANCING THE SHALE INTO DIRECT HEAT TRANSFER RELATION TO A SERIES OF ELONGATED HEATING ELEMENTS ARRANGED PARALLEL TO THE PATH OF TRAVEL OF THE SHALE WHILE EXCLUDING AIR FROM THE PREHEAT AND DISTILLATION ZONES, AND THEREAFTER POSITIVELY ADVANCING THE SHALE FROM THE DISTILLATION ZONE TO A HEAT EXCHANGE ZONE IN WHICH THE SHALE ROCK IS COMBUSTED TO PRODUCE ADDITIONAL HEAT ENERGY. 